U.S. patent application number 12/518979 was filed with the patent office on 2010-05-27 for wire harnessing tape.
This patent application is currently assigned to SCAPA FRANCE. Invention is credited to Jayne Elliot, Robert Mayan, Arnaud Riva.
Application Number | 20100129650 12/518979 |
Document ID | / |
Family ID | 37770337 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100129650 |
Kind Code |
A1 |
Mayan; Robert ; et
al. |
May 27, 2010 |
WIRE HARNESSING TAPE
Abstract
The present invention relates to an adhesive tape comprising a
wet-laid nonwoven backing material and an adhesive which is useful
as a wire harnessing tape in automotive industry. The nonwoven
comprises synthetic fibers, cellulose fibers and a binder.
Moreover, a process for manufacturing the adhesive tape is
provided.
Inventors: |
Mayan; Robert; (Valence,
FR) ; Riva; Arnaud; (Rumilly, FR) ; Elliot;
Jayne; (Cheshire, GB) |
Correspondence
Address: |
Pabst Patent Group LLP
1545 PEACHTREE STREET NE, SUITE 320
ATLANTA
GA
30309
US
|
Assignee: |
SCAPA FRANCE
|
Family ID: |
37770337 |
Appl. No.: |
12/518979 |
Filed: |
December 4, 2007 |
PCT Filed: |
December 4, 2007 |
PCT NO: |
PCT/EP07/63249 |
371 Date: |
December 3, 2009 |
Current U.S.
Class: |
428/339 ;
428/343 |
Current CPC
Class: |
C09J 2401/006 20130101;
C09J 2203/302 20130101; C09J 2400/263 20130101; C09J 7/21 20180101;
C09J 7/205 20180101; Y10T 428/28 20150115; Y10T 428/269 20150115;
C09J 2467/006 20130101 |
Class at
Publication: |
428/339 ;
428/343 |
International
Class: |
C09J 7/04 20060101
C09J007/04; B32B 5/00 20060101 B32B005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2006 |
EP |
06291914.7 |
Claims
1. An adhesive tape comprising (a) a wet-laid nonwoven backing
material, comprising synthetic fibers and cellulose fibers wherein
the ratio of synthetic to cellulose fibers is 4:1 to 1:4, and the
nonwoven backing material is chemically bonded; and (b) an
adhesive.
2. The adhesive tape according to claim 1, characterized in that
the synthetic fibers are polyester fibers.
3. The adhesive tape according to claim 1, characterized in that
the cellulose fibers are wood pulp fibers.
4. The adhesive tape according to claim 1, characterized in that
the weight ratio of fibers to the binders is 80:20 to 20:80.
5. (canceled)
6. The adhesive tape according to claim 1, characterized in that
the fiber length of the cellulose fibers and synthetic fibers is in
the range of 1 to 20 mm.
7. The adhesive tape according to claim 1, characterized in that
the chemical binder comprises one or more binding agents selected
from acrylic homopolymers, acrylic copolymers and/or ethylene-vinyl
acetate copolymers.
8. The adhesive tape according to claim 7, characterized in that
the chemical binder is a mixture of an acrylic polymer and a
styrene-acrylic copolymer.
9. The adhesive tape according to claim 8, characterized in that
the ratio of the acrylic polymer to the styrene-acrylic copolymer
is 4:1 to 1:4.
10. The adhesive tape according to claim 1, characterized in that
the wet-laid nonwoven is consolidated by hydroentanglement.
11. The adhesive tape according to claim 1, characterized in that
the adhesive is selected from acrylates and natural or synthetic
rubber compositions.
12. A process for manufacturing an adhesive tape as defined in
claim 1 comprising the step of coating the wet-laid nonwoven with
the adhesive.
13. (canceled)
Description
[0001] The present invention relates to an adhesive tape containing
a wet-laid nonwoven as a backing material. The tape is particularly
useful as a wire harnessing tape for use in the automotive
industry.
BACKGROUND
[0002] Different adhesives are applied to specialty backings and
carriers, such as films, foams and textiles, to provide products
that meet a variety of requirements. Non-woven tapes in the prior
art that do not use a binder to chemically bind the non-woven
fibers have been described. For example, WO 2004/058177 describes a
tufted fibrous web that can be used as a "tacky adhesive based
cloth". DE 200 06 192 describes a material with a foam and
non-woven layer, the non-woven layer being composed of a mixture of
cotton and synthetic polymers. DE 44 42 092 describes a
stitch-bonded tape, the carrier of which can be made up of
non-woven polyester, polypropylene or cotton fibers held together
with a lacquer.
[0003] Pressure sensitive adhesive (PSA) tapes are widely used in
automotive industry to manufacture wire harness assemblies.
Although PSA tapes account for just a fraction of the total
component cost, they are critical to the manufacturing of
cost-effective automotive wire harness assembly. In 2003, more than
150 million square meters of wire harness tape was used by the
automotive industry around the world.
[0004] The average vehicle's wire harness system consists of
approximately 1000 meters of wire and runs from the engine
compartment through the passenger area to the trunk.
[0005] These distinct environments require tapes with diverse
performance capabilities. For example, tapes used in the engine
compartment must resist fluids and high temperatures. Harnesses in
the interior instrument panel, door panel and overhead areas
require tapes that attenuate noise, vibration and harshness, to
minimize squeaks and rattles caused by wire harness movement at
high speeds.
[0006] Temperature is a major concern in automotive applications.
For wire harness assemblies, automotive temperatures are typically
segmented into four ranges. T1 applications do not exceed
85.degree. C. T2 applications range from 86 to 105.degree. C. T3
includes temperatures ranging from 106 to 125.degree. C., and T4
applications involve temperatures of 126 to 150.degree. C.
[0007] Generally, tapes that use rubber and modified rubber
adhesives are best for T1 and T2 applications. Acrylic adhesives
perform well in the T3/T4 temperature range. Silicones are ideal
for temperatures of T4 and higher.
[0008] Several types of backings are used on automotive wire
harness tapes. Backing materials are selected based on the
requirements of the application. Common backings include PVC,
cotton cloth, coated cloth, felt, polyester cloth and glass cloth.
Some backings and adhesive systems are also flame-retardant.
[0009] Adhesive-coated PVC is widely used for termination and clip
retention, where squeak and rattle issues are not a concern.
[0010] Cloth tapes provide the most economical squeak and rattle
protection and are used for clip retention and harness wrapping
inside doors, instrument panels and overhead areas. Coated cloth
tapes are used for splice protection of wire terminations and
breakouts, due to their high moisture resistance. The latest cloth
tapes provide significantly improved abrasion resistance compared
with PVC tapes. Flame-retardant cloth tapes offer performance
benefits in engine compartment applications.
[0011] According to a concise survey carried out by R. C. Lilly in
2003 (Web Exclusive: Pressure Sensitive Tapes in Wire Harness
Assembly, Ronald C. Lilly, Jun. 1, 2003,
www.assemblymag.com/CDA/Articles/Web_Exclusive/e9a1a455ed5
c9010VgnVCM100000f932a8c0): "Adhesive tapes made of felt and
non-woven materials provide the greatest noise protection, but are
also the most expensive. They are used sparingly in applications
that require extreme quiet, such as instrument panels and overhead
harnesses in luxury vehicles."
[0012] The PSA tapes used in automotive harness assemblies are
selected based on the application, the location of the assembly
within the vehicle, and performance requirements. Tape selection is
done by the harness manufacturer, conforming to OEM (original
equipment manufacturer) specifications to ensure reliable vehicle
operation and vehicle safety throughout its lifetime.
[0013] These tapes have to meet specific requirements to perform
well during application and a life cycle of a car. Among the
functions these tapes have to fulfill the most important ones are
containment of cables and splicing. Three main ways of wrapping
cables to build a wire harness are known: (i) spiral, better
described as helicoidal, (ii) flag, and (iii) clip wrapping.
Depending on the required level of sound dampening, abrasion
resistance and temperature shielding, one of these wrapping
techniques will be used. During the production of wire harnesses,
tapes are mainly applied manually and therefore must have defined
and consistent unwinding characteristics, good pliability and
flexibility and must be tearable by hand. Some operators tear in
crosswise direction, others tend to break the tape by stretching
longitudinally. When stretched, tapes commonly exhibit a behavior
described as curling, where the stress leads to deformation in U-
or S-shape. Curling increases the risk of flagging and thus has to
be minimized.
[0014] During the useful life of a car, pressure sensitive adhesive
tapes must maintain excellent adhesion to cables over many years.
In addition to strong adhesion to a wide range of cables,
appropriate mechanical properties are required. Excellent aging
resistance, resistance to automotive fluids, sound dampening and an
ability to withstand abrasion are key properties. If tapes are
employed in the passenger compartment, low odor and fogging
properties are increasingly important. Ultimately, a harnessing
tape product has to meet cost expectations of users.
[0015] Adhesive tapes for automotive wire harnessing applications
need to meet a wide range of performance criteria during
application and during the life cycle of a vehicle. The following
Table 1 lists the most important customer needs and translates them
into physical and chemical parameters. It is apparent that the
composition of the backing material critically influences every
aspect of the final product's performance.
TABLE-US-00001 TABLE 1 Metrics Tensile & Tensile &
elongation elongation Backing Defined Coating Choice of Backing
Abrasion Backing Sound Burn Needs CD MD thickness unwindding weight
adhesive composition test weight dampening test Hand .cndot.
.cndot. .cndot. .cndot. .cndot. tearable Curling .cndot. .cndot.
.cndot. .cndot. .cndot. Flexibility .cndot. .cndot. .cndot. .cndot.
.cndot. and pliability Abrasion .cndot. .cndot. resistance Good
sound .cndot. .cndot. dampening Consistent .cndot. .cndot. .cndot.
unwind Thermal .cndot. .cndot. stability T3 Black color .cndot.
Adhesion .cndot. .cndot. Aging .cndot. .cndot. resistance No
flagging .cndot. .cndot. .cndot. .cndot. Cost .cndot. .cndot.
.cndot. .cndot. .cndot. .cndot. .cndot. .cndot. constraint No
fogging .cndot. .cndot. .cndot. Range of .cndot. lengths &
widths Good .cndot. .cndot. cohesion Burn .cndot. .cndot. .cndot.
.cndot. .cndot. .cndot. behavior No banned .cndot. .cndot. .cndot.
substances Adhesion .cndot. .cndot. .cndot. .cndot. backside
[0016] Tapes based on woven materials, stitchbonded fabrics like
Maliwat (EP 0 716 137) or needle punched nonwovens like Malivlies
(EP 0 716 136), have been known on the market for several years.
Woven or knitted fabrics offer excellent suitability for harnessing
tapes, but are less cost-efficient than nonwovens due to a more
complex and slower manufacturing process. Today, their use is
becoming more and more uneconomical.
[0017] The use of wet-laid technology to produce tape materials for
niche applications has been known in the industry for a long time.
This type of nonwoven has been used for years in the area of cable
wrapping tapes, i.e. non-adhesive strips of considerable length. As
early as 1964, Copeland described in U.S. Pat. No. 3,121,021 the
advantages of chemically bonded nonwovens for medical tape
applications. According to this patent document, suitable carrier
materials can also be made by wet-laid procedures. The resulting
product, Micropore.RTM. was commercialized by 3M for more than 40
years.
[0018] The manufacture of wet-laid nonwoven is described in detail
by B. P. Thomas in 1993 (Thomas, B. P., A Review of Wet-Laid
Nonwovens: Manufacturing and Markets, INDA-TECH 93, 247-264
(1993)). According to this comprehensive review, wet-laid nonwovens
are produced from a process which originates from paper making.
Briefly, and as used in this invention, an aqueous solution
containing dispersed synthetic and/or cellulose fibers is deposited
onto a screen or roller where the water is stripped resulting in a
layer of fibers. If cellulose fibers are used in the wet laying
process, they swell and become soft and flexible whereas synthetic
fibers such as polyester remain stiff and straight. When forming a
web, the soft and flexible cellulose fibers give a high degree of
entanglement with the synthetic fibers. This increased entanglement
imparts unique properties to a wet-laid web as compared to other
web manufacturing processes such as dry-laying. This softening
effect of cellulose fibers is described in Wood Science and
Technology, 25(2), 1991, page 135.
[0019] Fibers for use in wet-laids fall into various groups. The
most basic distinction is between natural and man-made fibers.
Natural cellulose fibers are found in wood together with other
materials such as lignin and hemicellulose. Employed after
separation from these other materials and purification, they are
often named wood pulp fibers.
[0020] Cellulose is the most abundant naturally occurring organic
substance, being found as the principal component of cell walls in
higher plants where it provides the main structural feature. Cotton
is almost pure cellulose (98%); flax contains 80% and wood 40-50%
cellulose (with the remaining 50% made up from other complex
polysaccharides). The special properties of cellulose result from
the association of the long molecular chains to form fibers called
microfibrils. The microfibrils associate to form larger fibers,
which can be separated from other plant materials during the
pulping process.
[0021] Man-made materials include cellulosics and synthetic fibers.
Cellulosics are derived from cellulose by chemical modification.
Examples include viscose rayon, cellulose acetate and other
modified cellulose fibers. Although these are defined as man-made,
they are not pure synthetics since the basic component, cellulose,
is naturally fibrous. Synthetics are produced by full
polymerization from monomeric building blocks and include polyester
(e.g., Diolen.RTM., Trevira.RTM.), polyamide (e.g., nylon),
acrylics (e.g., Orlon.RTM.) and polyurethane (e.g., Lycra.RTM.,
Elastan.RTM.).
[0022] U.S. Pat. No. 5,631,073 describes in great detail the
benefits of employing nonwovens made of man-made fibers and
chemical binders for medical applications. These are used for
affixation of articles such as dressings and tubing and as backings
for first-aid and island-type dressings. Particularly preferred
constructions are: a nonwoven consisting of 80% polyester staple
fibers and 20% of polyester binder fibers pattern-embossed and
afterwards saturated with water-based acrylic copolymer binder. In
a second preferred embodiment, this nonwoven is hydroentangled
prior to being pattern-embossed.
[0023] Products for medical applications need to be finger or hand
tearable. Other essential physical characteristics of the nonwoven
include dry and wet strength, conformability, tearability in web
direction and a uniformity of strength both in web and cross web
direction.
[0024] The above-outlined requirements for an automotive tape
demonstrate that the performance needed is fundamentally different
from those of a medical tape.
SUMMARY
[0025] An object of the present invention is to provide an adhesive
tape which demonstrates excellent performance in the field of wire
harnessing and which can be produced in a cost-efficient way. This
object is achieved by providing an adhesive tape comprising, a
wet-laid nonwoven backing material comprising synthetic fibers,
cellulose fibers and a binder, and an adhesive. Moreover, a process
for manufacturing the adhesive tape is provided.
DETAILED DESCRIPTION
The Nonwoven Backing Material
[0026] Surprisingly, it was found that a nonwoven comprising
cellulose fibers, especially wood pulp fibers, synthetic fibers,
especially polyester fibers, and a binder provides a backing
material for adhesive tapes with excellent properties for
automotive tape applications, in particular for automotive wire
harness applications.
[0027] The term "cellulose fibers", as used herein, refers for
example to cellulose fibers found in plants, i.e. natural cellulose
fiber. These fibers do not undergo any chemical modifications
before used in nonwoven and other industrial manufacturing
processes. Thus, cellulose fibers, as used in the present
invention, are distinguished from man-made cellulosics such as
viscose (rayon), cellulose acetate and other modified cellulose
fibers which are derivable from (natural) cellulose by chemical
modification.
[0028] The term "wood pulp fibers" refers to cellulose fibers found
in wood together with other materials such as lignin and
hemicellulose which are removed prior to use.
[0029] The main parameters for optimizing the nonwoven used as a
backing material in the adhesive tape of the present invention are
the type, the quantities and the proportion of fiber and binder
used. In a preferred embodiment of the present invention, polyester
fibers are used as synthetic fibers in the nonwoven backing
material. These polyester fibers are preferably polyethylene
terephthalate (PET) or poly lactic acid (PLA) which may be produced
by melt spinning.
[0030] With regard to the optimum balance of pliability and
abrasion resistance, the ratio of synthetic to natural fibers in
the adhesive tape of the present invention is preferably 4:1 to 1:4
and more preferably 3:1 to 1:3, whereas the ratio of fibers to the
binder is preferably 80:20 to 20:80 and more preferably 70:30 to
30:70. Higher amounts of the binder confer more abrasion resistance
to the adhesive tapes.
[0031] From the viewpoint of optimizing the tearability and tensile
strength, the fiber length of the synthetic and cellulose fibers is
preferably in the range of 1 to 20 mm, more preferably in the range
of 2 to 15 mm.
[0032] The weights (or fineness) of both the synthetic and the
cellulose fibers are preferably in the range of 0.7 to 5.5 dtex,
more preferably in the range of 1 to 4 dtex.
[0033] As a chemical binder, one or more binding agents selected
from acrylic homopolymers or copolymers can be used. Suitable
binders can be acquired from well known sources like BASF
(Acronal.RTM. range); Rohm & Haas (Rhoplex.RTM. and Primal.RTM.
range); Celanese (Nacrylic.RTM. products) and Icap-Sira
(Acrilem.RTM. range). Cohesion of the wet-laid nonwoven can be
further improved by use of self-crosslinking binders or by addition
of external crosslinkers.
[0034] Besides acrylic-based binders, ethylene-vinyl acetate
copolymers can be used, in cases where higher cohesion of the
nonwoven is required. Examples of suitable grades are those
available from Celanese (6161 RD Geleen, Netherlands) under the
trade names Dur-O-Set.RTM. and Vinamul.RTM..
[0035] Preferably, the binder is a mixture of an acrylic polymer
and a styrene-acrylic copolymer. More preferably, the weight ratio
of the acrylic polymer to the styrene-acrylic copolymer is 4:1 to
1:4. Suitable styrene-acrylic binding agents include Acronal.RTM.
5530, Acronal.RTM. NX 5818, Acronal.RTM. 296 D or Acrilem.RTM.
ST41. As acrylic binding agents, acrylate or acrylate/acrylonitrile
copolymers such as Acrilem.RTM. ES8, Acrilem.RTM. 6090,
Acronal.RTM. 50 D, Acronal.RTM. LA 471 S, Rhoplex.RTM. GL-618 or
Rhoplex.RTM. HA-8 can be employed.
[0036] Advantages of blending a styrene-acrylic and an acrylic
binding agent are realized, as each type of binding agent imparts
different beneficial properties. Styrene-acrylic binding agents are
stiffer, harder and provide better abrasion resistance, while
acrylic polymers are softer, more elastic and provide elasticity
and pliability to the nonwoven. More importantly, the considerably
higher glass transition temperature (T.sub.g) of the
styrene-acrylics provides the required stability during use at
higher temperature under T3 and T4 conditions. Blending both types
of binding agent and varying the ratio of both components provides
a route to optimizing the performance of the nonwoven and the final
harnessing tape product.
[0037] The preferred weight of the nonwoven is between 10 and 140
g/m.sup.2, since mechanical properties like tensile strength,
elongation at tear, stiffness and flexibility in this range allow
construction of an automotive harnessing tape with the desired
performance.
[0038] The wet-laid nonwoven used as a backing material in the
adhesive tape of the present invention can be manufactured
according to the method described by B. A. Thomas in 1993 (Thomas,
B. F., A Review of Wet-Laid Nonwovens: Manufacturing and Markets,
INDA-TECH 93, 247-264 (1993)). The fundamental process for
manufacturing wet-laid nonwovens, which can be used to produce the
wet-laid nonwoven of the present invention, can be roughly divided
into three separate steps.
[0039] Firstly, fibers to be used for the nonwoven are dispersed in
water in a total concentration of 0.05 to 0.5% by weight. If a mix
of cellulose fibers and synthetic fibers is used, good dispersion
and homogeneity of the water dispersion has to be achieved. A
number of chemical additives have been developed to aid dispersion
and maintain it through the storage system. In addition, foam
generation has to be minimized to avoid thin patches or holes in
the web.
[0040] In the second step, the dispersed fibers are deposited on a
screen or cylinder, and by stripping the water, a layer of fibers
is created. If synthetic fibers are part of the formulation, all
natural cohesive tendencies through hydrogen bonding are lost.
[0041] In the third step, bonding is performed. The nonwoven of the
present invention is chemically bonded. In addition to chemical
bonding, mechanical bonding and/or thermal bonding can be used in
the process for manufacturing the nonwoven of the present
invention
[0042] Chemical bonding uses binders to provide the required
cohesion and strength to the nonwoven as described, for example, in
EP 0 995 783 A and U.S. Pat. No. 5,631,073. It can be applied by
deposition, spraying, saturation, coating or sizing during or after
web formation. Optionally, binders with crosslinking capability can
be used.
[0043] The cohesion of nonwoven samples was tested by peeling a
strip of tape from the backside of an adhesive coated specimen in
an angle of 180.degree., measuring the force required to remove the
tape and noting if the nonwoven sample is destroyed. Using tapes
with more and more aggressive adhesion, a point is reached where
the wet-laid nonwoven splits, i.e. a part of the nonwoven remains
on the tape pulled away. This value corresponds to the cohesive
strength of the wet-laid.
[0044] Table 2 demonstrates the different cohesion strength
behaviors depending on the binder used. All samples consisted of
30% Polyester, 40% Wood pulp fibers and 30% binder. Although the
sample with ethylene-vinyl acetate (EVA) binder is thicker and as
such more prone to cohesive failure, the cohesion value achieved is
superior to the corresponding samples with acrylic binder.
TABLE-US-00002 TABLE 2 Sample 1 2 3 Weight (g/m.sup.2) 52 57 68
Binder Acrylic Acrylic EVA T.sub.g -23.degree. C. -4.degree. C.
-6.degree. C. Cohesive strength (N/cm) 2.5 3 4.5
[0045] Mechanical bonding can be done either through natural
entanglement during web formation or through a forced entanglement
such as hydroentanglement. Both methods have been described in U.S.
Pat. No. 5,631,073 in detail. In one embodiment of the adhesive
tape of the present invention, the nonwoven is further consolidated
by hydroentanglement.
[0046] Hydroentanglement is achieved by placing the web between
mesh screens and subsequently passing high pressure water jets
through the screen and the web. Forced entanglement such as
hydroentanglement provides higher levels of cohesion; however, it
introduces patterns to the surface of the product. More
importantly, this process weakens the nonwoven in longitudinal and
transversal directions. The use of water or air jets to bond
nonwovens for harnessing applications has been described in EP 1
123 958 A.
[0047] A third type of bonding which may be used in the process for
manufacturing the nonwoven of the present invention is known as
thermal bonding. Here, typically at least two fibers of different
melting points are submitted to air drying, infrared bonding, hot
calendaring and embossing to partially melt the fibers with lower
melting point. For example, the binder fibers with a core-sheath
construction can be used. These fibers consist of a meltable sheath
and a core, which does not melt under the chosen processing
conditions. As described in U.S. Pat. No. 5,631,073, combinations
of different bonding techniques can be used, like hot pattern
embossing of a hydroentangled nonwoven.
[0048] Essential characteristics of a polymer which can be employed
for binder fibers are efficient melt flow, good adhesion to the
carrier fiber, a lower melting point than the carrier fiber and
desired stiffness or elasticity. Single-component and bi-component
binder fibers are most widely used in thermal bonding of nonwovens.
Single-component fibers are the least sophisticated and most
economical ones. The major disadvantage of single-component fibers
is the narrow temperature range useful for bonding. If the
temperature is too low, there is inadequate bond strength. If it is
too high, the web will melt excessively and flexibility and
pliability will suffer. Single-component fibers suitable for
papermaking and wet-laid nonwovens include polyvinyl alcohol, e.g.
Kuralon.RTM., and ethylene-vinyl alcohol fibers. Both types are
commercially available from Kuraray Europe GmbH, Building F821,
Hoechst Industrial Park, 65926 Frankfurt am Main, Germany.
[0049] Bi-component fibers offer a much wider acceptable
temperature range for bonding. The high melting portion of the
fiber maintains the integrity of the web, while the low melting
point portion melts and bonds with other fibers at the fiber
crossover points. Most common configuration is the sheath-core
type. The following combinations are widely used: [0050] Polyester
core (melt point: 250.degree. C.) with copolyester sheath (melting
points of 110.degree. C. to 220.degree. C.) [0051] Polyester core
(melt point: 250.degree. C.) with polyethylene sheath (melting
point: 130.degree. C.).degree. [0052] Polypropylene core (melting
point: 175.degree. C.) with polyethylene sheath (melting point:
130.degree. C.) [0053] Polyester core (melting point: 250.degree.
C.) with ethylene-vinyl alcohol sheath (melting point: 100.degree.
C.)
[0054] Fiber Innovation Technology, 398 Innovation Drive, Johnson
City, Tenn. 37604, USA, supplies a range of suitable products.
[0055] Beyond the choice of fibers, forming and bonding technology,
other nonfibrous fillers and nonbonding additives can be added.
These additives introduce features like color, hydrophobicity,
release (i.e. reduced adhesion at the backside of the backing
material) and flame retardancy.
[0056] Colors for nonwovens can be divided into dyes and pigments.
Dyes have substantivity for fibers, meaning they are attracted from
their application media by the fibrous substrate. Pigments are
applied from a latex medium. Both dyes and pigments can be applied
at various stages of the nonwoven process, starting from the
polymer or pulp of fibers prior to web formation. In certain
polymers such as polyester, dyes and pigments can be added as a
concentrate to the polymer immediately prior to extrusion. This
process is referred to as producer coloration or melt dyeing.
Conventional dyeing is a wet process and is time, energy and
cost-intensive. Wherever possible, coloring of the web is combined
with the wet processes necessary for the bonding. Preferably, the
dye is added to the dispersion containing the bonding agent. The
binder adheres to the surface of the fibers and imparts the
excellent non-fading properties which pigments are noted for.
Dyeing can also be carried out at a later stage. The nonwoven
fabric is then treated like a woven or knitted fabric and dyed in a
traditional way.
[0057] For harnessing tapes, black color is mandatory, so
well-known black pigments like carbon black (available as color
black or Printex.RTM. from Degussa) and ferric oxide pigments are
added to the binder to provide the appropriate color.
Alternatively, black colored fibers can be employed in the
manufacture of the textile.
[0058] Flame retardancy of the tape end-product can be greatly
enhanced by addition of suitable compounds. Boylan and Matelan
(Nonwoven Binders Innovative Solutions: Providing Aqueous Barrier
and Flame Retardant Properties for Nonwovens, J. R. Boylan, D. A.
Matelan, Air Products Polymers, L.P. 7201 Hamilton Boulevard,
Allentown, Pa. 18195-1501, Pub. No. 151-03-029-GLB, 2003) describe
the effects of combining halogenated polymers like ethylene-vinyl
chloride copolymers and inorganic or phosphorous flame retardants.
Airflex.RTM. 4530 and hydrated compounds like alumina trihydrate or
magnesium hydroxide can be blended and applied to the nonwoven.
DIOFAN.RTM. A 585 from Solvay S.A. is an anionic aqueous dispersion
of vinylidene chloride/butyl acrylate/methyl actylate terpolymer
intended to be used as flame retardant binder for textiles and
nonwovens. U.S. Pat. No. 6,344,514 discloses a formulated binder
consisting of styrene-butadiene latices and diammonium phosphate.
Flame retardancy of Vycar.RTM. 590.times.4 of Noveon (available in
Europe from VELOX GmbH, D-20457 Hamburg), which is a plasticized
vinyl chloride copolymer emulsion, is significantly enhanced when
the latex is compounded with 2 to 5 parts Antimony oxide per 100
parts latex solids. Preferably, retardants with different chemical
compositions are combined to act in a synergistic way. All of the
above mentioned substances and combinations thereof can be used to
impart the desired level of flame retardancy to the tape
end-product.
[0059] Harness tapes are supplied to the end-user as self-wound
rolls, i.e. the tape is wound directly onto itself, with no
interleaving or liner between the backing and the adhesive and the
next layer of tape. Therefore consistent unwinding of the roll is
of major importance. The force required to unwind tape from the
roll is governed by the adhesion of the adhesive layer to the
underlying external surface to the nonwoven backing. This adhesion
can be controlled by lowering the surface energy of the nonwoven by
applying so called release agents, low adhesion backsize (LAB)
materials or repellents. Suitable compounds include fluorocarbons,
silicones or hydrocarbon chemicals applied to the nonwoven by
sizing, spraying, Foulard or other suitable processes. Foulard
application employs aqueous dispersions of repellents in
concentrations between 0.1 vol % and 10 vol %. By adjusting the
amount of the release agent, the adhesion to the backside and thus
the unwinding force can be controlled and adjusted to the desired
level. Suitable repellents include Zonyl.RTM. available from
DuPont, Oleophobol.RTM. available from Ciba SC, Nuva.RTM. available
from Clariant and a polyvinylstearate-carbamate copolymer Icafinish
CS16.RTM. from ICAP-Sira.
Adhesive
[0060] Pressure-sensitive adhesives of various chemical
compositions can be employed in the present invention. Acrylates
and natural or synthetic rubber compositions are especially
suitable, either in the form of solvent-based, water-based or
hot-melt adhesives. Appropriate pressure-sensitive adhesives are
described in D. Satas: Handbook of Pressure Sensitive Adhesive
Technology 2nd ed. (Van Nostrand Reinhold, New York, 1989) and are
available from a range of well known suppliers like National Starch
& Chemical (Duro-Tak.RTM.), Rohm & Haas, Lucite, Ashland
Chemical, Cytec and ICAP-Sira. Important suppliers of hot melt
adhesives are BASF, Collano, H. B. Fuller or Novamelt. Hot melt
adhesives can require crosslinking to withstand higher
temperatures. Particularly suitable is a range of UV-curable
acrylic hot melt adhesives offered by Collano AG under the brand
name Collano UV N1.RTM..
[0061] To optimize its properties, the adhesive may be blended with
one or more additives such as tackifiers, plasticizers, fillers,
pigments, UV absorbers, light stabilizers, aging inhibitors,
crosslinking agents, crosslinking promoters or elastomers.
[0062] Suitable elastomers for blending include EPDM (ethylene
propylene diene monomer) or EPM (ethylene propylene monomer)
rubber, polyisobutylene, butyl rubber, ethylene-vinyl acetate,
hydrogenated block copolymers of diener, including and not limited
to styrene-isoprene-styrene (SIS), styrene-ethylene-butadiene
(SEE), styrene-ethylene-butadiene-styrene (SEM),
styrene-ethylene-butadiene-styrene/styrene-ethylene-butadiene
(SEBS/SEB), styrene-butadiene-styrene (SES),
styrene-isoprene-butadiene-styrene (SIBS), and acrylate copolymers
such as ACM (ethyl butyl acrylate copolymer).
[0063] Suitable tackifiers include hydrocarbon resins (e.g. of
unsaturated C5 or C7 monomers), terpene-phenol resins, terpene
resins from raw materials such as pinene, aromatic resins such as
coumarone-indene resins, or resins of styrene or .alpha.-methyl
styrene, such as rosin and its derivatives such as
disproportionated, dimerized or esterified resins, tall oil and its
derivatives and also others, as listed in Ullmann's Encyclopedia of
Industrial Chemistry, 5.sup.th Edition, VCH, Weinheim 1997,
Weinheim. Particularly suitable are aging-resistant fully saturated
resins without olefinic double bonds.
[0064] Examples of suitable fillers and pigments are carbon black,
titanium dioxide, calcium carbonate, zinc carbonate, zinc oxide,
silicates and silica.
[0065] Suitable UV absorbers, light stabilizers and aging
inhibitors are well known in the art. Examples include antioxidant
Vulkanox.RTM. BKF (2,2'-methylene-bis-(4-methyl-6-t-butylphenol)
and antioxidant Irganox.RTM. 1010 (Pentaerythritol
tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) which
can be added by 1% by weight relative to the dry adhesive to
improve stability of the adhesive.
[0066] Examples of suitable plasticizers include aliphatic,
cycloaliphatic and aromatic mineral oils, diesters or polyesters of
phthalic acid, trimellitic acid or adipic acid, liquid rubbers
(e.g., nitrile rubbers or polyisoprene rubbers), liquid polymers of
butene and/or isobutene, acrylates, polyvinyl ethers, liquid resins
and soft resins based on the raw materials for tackifier resins,
lanoline and other waxes. Aging-stable plasticizers without an
olefinic double bond are particularly suitable.
[0067] Crosslinking can be achieved by chemical reaction, EB- or
UV-curing or addition of sulphur curatives or organometallic
coupling agents based on polyvalent metal ions like aluminum,
zirconium and titanium. The Tyzor.RTM. range by DuPont is widely
used. Examples of further crosslinking agents include phenolic
resins (which may be halogenated), melamine and formaldehyde
resins. Suitable crosslinking promoters include maleimides, allyl
esters such as triallyl cyanurate, and polyfunctional esters of
acrylic and methacrylic acid. Use of crosslinked adhesives is
especially preferred for high temperature applications of the tape,
especially in engine compartments.
[0068] Adhesive coating weights used in the present invention are
preferably in the range of 20 to 200 g/m.sup.2, Within this range,
desired pressure sensitive adhesion properties can be obtained with
an acrylic copolymer, or with a synthetic or a natural rubber
adhesive well known in the industry. More preferably, the adhesive
coating weights are in the range of 30 to 150 g/m.sup.2.
[0069] Adhesive tapes are manufactured by coating backing materials
with pressure sensitive adhesives. The main processes used are
coating of hot melt or liquid adhesives, either by transfer or
direct coating. Transfer coating uses an intermediate carrier like
silicone paper or film or a siliconized belt to dry or partially
dry the adhesive layer before laminating it to the backing. Direct
coating transfers dissolved or molten adhesive on the carrier, with
subsequent cooling or evaporation of solvent. Commonly, direct
coating is preferred for economical reasons, since there is no need
for intermediate process liners.
[0070] A wide range of coating techniques to apply adhesives to
filmic or textile backings is well known in the industry. The
following techniques are most often used: gap coating i.e. knife
over roll, roll over roll, floating knife, knife over blanket; air
knife coating; curtain coating; rotary screen coating; reverse roll
coating; gravure coating; metering rod (Meyer bar) coating; slot
die (Slot, Extrusion) coating and hot melt coating. All of these
coating methods can be applied to manufacture the aforementioned
tape of the present invention. Most preferably, gap coating is
used. This gives best results concerning anchorage of the adhesive
into the backing while at the same time avoiding striking through
during the coating step.
EXAMPLES
[0071] The following established standards were used to determine
physical properties of the adhesive tape.
[0072] Measurement of breaking strength: EN 1940 Self adhesive
tapes.
[0073] Measurement of elongation at break: EN 1941 Self adhesive
tapes.
[0074] Abrasion resistance: ISO 6722 (2002) Chapter "scrape
abrasion" with 6 mm diameter mandrel, identical to chapter 7.11 of
"Harness Tape Performance Specification" ES-XU5T-1A303-AA of Ford
Motor Co.
[0075] Adhesion to backside/unwind force, Adhesion data: AFERA
4001, corresponding to DIN EN 1939 Self adhesive tapes:
Determination of peel adhesion properties.
[0076] Sound dampening performance: PSA test method 9645871099D
"Protection faisceau rubans".
[0077] Hand tearability: Chapter 7.3.6 of the established standard
"Adhesive tapes for wiring harnesses in motor vehicles" LV312 of
Audi AG, BMW AG, DaimlerChrysler AG, Porsche AG and Volkswagen
AG.
[0078] According to LV312, the tear properties are assessed by a
panel of individuals who are familiar with adhesive tapes,
especially for automotive harnessing applications. The group
evaluates these tapes for conformability, ease of tear, tear
initiation, smoothness of the created edge, deformation of the tape
related to stress induced, so called curling, and the force
required to tear. Each of these characteristics is rated and the
overall performance is rated as "good manual tear-off property",
"limited manual tear-off property" or "no manual tear-off
property".
[0079] Conformability of the nonwoven was assessed by a Scapa
internal method. A rectangular test specimen of 5 cm length and 2
cm width was suspended on the edge of a plate, with 3 cm
protruding. The angle of the nonwovens deflection from the
horizontal is measured.
Example 1
[0080] A wet-laid nonwoven material consisting of 28% by weight
polyester fibers, 47% by weight wood pulp fibers and 25% by weight
binder was coated on a conventional knife over roll coating
equipment with 40 g/m.sup.2 Gelva GMS-2659.RTM., a solvent based
acrylic copolymer adhesive of Cytec Surface Specialties SA. After
drying, the resulting roll was converted using conventional
equipment to receive rolls of 1.9 cm width and 20 m length.
Example 2
[0081] A wet-laid nonwoven made of 45% by weight polyester, 20% by
weight wood pulp fibers and 35% by weight binder was coated on a
state of the art hot melt extruder with 60 g/m.sup.2 of synthetic
rubber hot melt adhesive. The obtained roll was converted using
conventional equipment to receive rolls of 1.9 cm width and 20 m
length.
Example 3
[0082] A wet-laid nonwoven material consisting of 34% by weight
polyester fibers, 17% by weight wood pulp fibers and 50% by weight
binder was coated on a conventional knife over roll coating
equipment with 30 g/m.sup.2 Gelva GMS-6144.RTM., a water-based
acrylic copolymer adhesive of Cytec Surface Specialties SA. After
drying, the resulting roll was converted using conventional
equipment to receive rolls of 1.9 cm width and 20 m length.
TABLE-US-00003 TABLE 3 Comparative Example 1 (tesa 51608) Example 1
Example 2 Example 3 Type of Maliwatt Wetlaid Wetlaid Wetlaid Fabric
Fibers 100% PES 28% PES 45% PES 34% PES wt % 47% Wood 20% Wood 17%
Wood Pulp Pulp Pulp Binder 25% Binder 35% Binder 50% Binder wt %
Release unknown Nuva FBN Nuva FBN Nuva FBN treatment [1 vol %]* [1
vol %] [1 vol %] *commercially available from Clariant (France),
69530 Brignais, France
TABLE-US-00004 TABLE 4 Compar- ative Ex- Ex- Ex- Example ample
ample ample Test Method 1 1 2 3 Backing weight 85 68.7 67.1 83.9
[g/m.sup.2] Backing AFERA 5006 275 260 250 227 thickness [.mu.m]
Color Black Black Black Noir Tensile NF EN 1940 34.6 27.4 39.1 24.8
strength MD [N/cm] Elongation MD NF EN 1941 20 19.9 17.8 19.4 [%]
Conformability Subjective 5 2 2 4 1 - very stiff 5 - Good
conformability [Index 1-5] Conformability Scapa 37 42 56 Deflection
internal Angle [Degree] Curling Subjective 4 5 5 5 1 - bad behavior
5 - good behavior [Index 1-5]
TABLE-US-00005 TABLE 5 After aging 10 days at 150.degree. C.
Compar- ative Ex- Ex- Ex- Example ample ample ample Test Method 1 1
2 3 Tensile NF EN 1940 18.5 26.7 22.8 strength MD Elongation NF EN
1941 9.5 15.3 17.8 MD Tensile NF EN 1940 19.4 25.4 21.9 strength CD
[N/cm] Elongation NF EN 1941 7.2 16.9 16.7 CD [%] Color No No No
change change change
TABLE-US-00006 TABLE 6 After aging 10 days at 175.degree. C.
Compar- ative Ex- Ex- Ex- Example ample ample ample Test Method 1 1
2 3 Tensile NF EN 1940 14 21.9 20.3 strength MD [N/cm] Elongation
NF EN 1941 9.5 11.6 15.8 MD [%] Tensile NF EN 1940 12.9 20.4 21.1
strength CD [N/cm] Elongation NF EN 1941 7.5 13 12.8 CD [%] Color
No No No change change change
TABLE-US-00007 TABLE 7 Compar- ative Ex- Ex- Ex- Example ample
ample ample Test Method 1 1 2 3 Adhesive coat 40 60 30 weight
[g/m.sup.2] Abrasion ISO 6722 62 8 51 109 resistance Renault/ISO
[Cycles] Sound PSA 8.3 9.1 10 dampening 9645871099D [dB] Adhesion
to AFERA 4001 5.1 2.6 1.74 1.09 backside/ unwind force [N/cm]
Tearability CD LV 312 2 1 1 1 1 - good manual tear- off property 2
- limited manual tear- off property 3 - no manual tear-off property
Cohesion of Subjective 4 5 5 4 backing 1 - fabric splitting 5 - no
fabric splitting [Index 1-5] Resistance to LV 312 automotive fluids
Motor oil Flag- OK OK ging Brake fluid Flag- OK OK ging Gasoil
Flag- OK OK ging
[0083] As shown in Tables 3 to 7, the adhesive tapes of Examples 1
to 3 show a similar performance to (Maliwat-product). Specifically,
it was found that the adhesive tape of the present invention has
excellent behavior in the following areas: tearability, curling,
flexibility, abrasion resistance, temperature stability, sound
dampening and resistance to automotive fluids. Furthermore, the
adhesive tapes of the present invention can be produced very
cost-efficiently. Hence, the overall balance of performance and
cost for the inventive adhesive tapes is better than that for the
tapes of the Comparative Example 1 (tesa 51608).
* * * * *
References